1. Field of the Invention
The present invention relates to a device combining ejection and self-cleaning filtration which is used as equipment for filtering air and ejection in molds for making mold cores blown in hot or cold boxes, as well as those for casting light-alloy parts by gravity or low pressure in metal molds.
2. Description of the Prior Art
For this type of equipment, two different devices are generally used, the first being a filtering element for letting the air escape at the moment of filling the mold. This filtering element is usually in the form of a porous or fritted plate, or one penetrated by a large number of holes or slits.
The second device is an ejector element consisting of a pusher guided in the mold and driven by an ejector device.
Among the drawbacks of the known devices are the multiplication of the filter-ejector elements and the difficulty in fabricating the filtering elements. Further, the slits or holes of the porous plate have a width or diameter of only some tenths of a mm (0.05 to 0.2), and therefore very rapid fouling of the slits or holes occurs, leading to a rapid decrease in the filtering area. In addition, guiding of the ejection elements is made difficult by the presence of sand and the mold temperature, and accordingly rapid deterioration of the molds takes place around the guides.